MPs are to debate the police raid on the House of Commons office of Tory frontbencher Damian Green amid deepening concern over the role played by Speaker Michael Martin.

Here is a timeline of events surrounding the arrest of the shadow immigration minister.

:: October 8: The Cabinet Office calls in the Metropolitan Police to investigate the Home Office leaks.

:: November 19: Junior Home Office official Christopher Galley is arrested and suspended from duty.

:: November 27: Shadow immigration minister Damian Green is arrested and held by the Metropolitan Police for nine hours, on suspicion of "conspiring to commit misconduct in a public office, and aiding and abetting, counselling or procuring misconduct in a public office".

Mr Green's home and his offices in Kent and in the Houses of Parliament are searched. He is released on bail until a date in February.

The senior civil servant at the Home Office, Permanent Secretary Sir David Normington, confirms that he called in the police following a number of leaks of sensitive information over "an extended period".

:: November 30: Home Secretary Jacqui Smith refuses to apologise for the arrest, saying the police had to be allowed to "follow the evidence where they need to" without interference from the Government.

But Commons Leader Harriet Harman says the processes allowing police to search MPs' offices in the House of Commons should be reviewed, adding that "big constitutional principles" are at stake.

:: December 1: Mr Galley insists he acted in the public interest. His lawyer Neil O'May says: "If there was ever a case of 'don't shoot the messenger', then this is it."

:: December 2: Scotland Yard announces an urgent review of its handling of the Whitehall leaks probe. British Transport Police chief Ian Johnston is set to deliver his interim findings to the Met's Acting Commissioner, Sir Paul Stephenson, within seven days, followed by a full report in two weeks.

:: December 3: In a dramatic statement to the Commons, the Speaker reveals that the police had neither a search warrant nor his permission to raid Mr Green's Commons office.

Constitutional expert Geoffrey Robertson QC says it is "unlawful" for officers to enter the Palace of Westminster without the Speaker's permission.

But the Metropolitan Police insist they had authority in the form of written consent from Serjeant at Arms Jill Pay, who is in charge of Commons security.

Mr Martin pledges that police will never again be allowed access to an MP's office or parliamentary papers without a warrant and the personal approval of the Speaker. He announces his intention to appoint a committee of seven experienced MPs to look into the seizure of Mr Green's papers, computer and mobile phone.

:: December 4: In a Commons statement, Jacqui Smith defends the decision to call in the police, arguing that the "systematic" leaking of sensitive Home Office documents could threaten national security.

Assistant Met Commissioner Bob Quick, the senior officer in charge of the leaks investigation, says his officers made clear to the House authorities that they needed their consent as they did not have a search warrant. His comments appear to directly contradict Mr Martin.

Liberal Democrat leader Nick Clegg announces that his MPs will not sit on the Speaker's committee to look into the Green affair. The boycott is sparked by ministers' plans to ensure a Labour majority on the seven-member committee and to delay its deliberations until after the conclusion of the police operation.

:: December 7: Mr Martin will stand for a third term according to the Sunday Times. A survey of 130 MPs by BBC Radio 4's The World This Weekend programme finds that 32 have lost confidence in him.